Patent GB-614840-A (GB)
Abstract: 614,840. Sewing-machines. SINGER MANUFACTURING CO. Aug. 6, 1946, No. 23208. Convention date, Nov. 19, 1945. [Class 112] In high-speed sewing-machines, particularly of the kind having a presser-foot and an upper feed-foot operating alternately, engagement of the foot or feet, with the work with adequate pressure is ensured by the use of a much greater spring pressure than usual, and in order to enable the operator to raise the foot or feet without difficulty the spring is relaxed and its pressure removed before lifting takes place, these operations being automatically performed in succession, by gearing of the Geneva type, on depression of the foot-lifting treadle. Feed ; presser-bars. In the machine described, a four-motion feed-dog beneath the work co-operates with a needle and an upper feed-foot 48, Fig. 3, the needle-bar 32 and feed-bar 47 being carried in a common guide 35 which is carried by a spindle 37, Fig, 1, and actuated through an arm 39 by an adjustable eccentric 44 on the needle-bar shaft 20. The presser-foot 57 is carried by a presser-bar 56 sliding in the frame behind the feed-bar and prevented from rotating by an arm 91 clamped on it and sliding on a fixed pin 89. Presser-bar and feed-bar, actuating-The upper end of the feed-bar 47 carries a cross-pin 50, Fig. 3, which is engaged by the forked end of a lever 52 pivoted at 53, and has cheeks engaging the sides of this lever to prevent rotation of the feed-bar. The lever 52 is counterbalanced, and at its centre of percussion it carries a spindle 60 to which is fixed at one end an arm 59 engaging a slot in the presser-bar and at the other end an arm 62 connected by a link to a counterbalanced arm on a rock-shaft 68 actuated by an adjustable eccentric 75 on the needle-bar shaft ; the mechanism thus lifts the feet 48, 57 alternately, using each as a fulcrum in turn. Pressure is applied to the feet by a lever 77 bearing on the lever 52, engaging under a knife-edge fulcrum 82, Fig. 1, and biased by a tension spring 78 adjustably attached to an arm 79 ; the arm 79 is pivoted at 134 and is normally held in position by a pair of toggle links 129, 130. The spring is as described in Specification 615,276, (Group XXXII).. Presser-bar and feed-bar, lifting, non-automatic- A treadle (not shown) is connected by a chain 106, Fig. 1, to an arm 107 pivoted at 109 and provided with a toothed segment 113 to actuate a pair of gears 114, 142, which have on their spindles Geneva drivers 117, 145 respectively. During the initial movement of the treadle, the pin 119 of the driver 117 rotates a member 121 fixed to a spindle 123 carrying an arm which is connected by a link 127 to the central pin of the toggle linkage, the toggle being thus broken to allow the arm 79 to relax the spring 78. On completion of this movement the member 121 is locked and the driver 145 then comes into play to actuate a member 148, pivoted at 149, to move a rack-bar 152 by means of a toothed segment on the member 148 ; this rack bar rotates a plug 84 carrying the knife-edge 82 to remove the latter from the lever 77, and a pin on the plug 84 engages a slot in a lever 160 which engages under the presser-bar guide arm 91 to lift the presser foot and feed-foot. The feet may be locked in their raised position by a pin 174 which can slide upwards in the frame against the arm 62 and retained in position by turning it. The parts are restored, when the treadle is released, by a pair of springs 166 attached by a flexible band to a cam on the spindle of the gear 114, these springs being able to re-tension the spring 78 by reason of the toggle linkage 129, 130. Threads, controlling. An arm 136 attached to the arm 79 carries at its end a cam which engages the pin of a thread-tension device to relieve the tension when the presser-foot and feed-foot are lifted. Further drawings of the feed mechanism are contained in Specification 615,276.